In recent years, angular velocity sensors have been used in automobiles. The angular velocity sensors particularly for this purpose have been required to be small and stable against sudden external vibrations, “disturbance” so as to have high reliability.
A conventional angular velocity sensor disclosed in U.S. Pat. No. 5,438,231 includes a tuning fork vibrator having a pair of vibrating arms coupled with each other at their lower ends with a coupling portion, drive electrodes formed on the vibrating arms to drive the arms in vibration directions and detection electrodes to detect the bending of the vibrating arms when an angular velocity is applied to the arms. The vibrating arms are designed to have a small driving resistance so as to decrease power consumption.
The vibrating arms designed only for the small driving resistance may cause unnecessary vibrations when receiving vibrations as disturbance at their natural vibration frequencies different from a fundamental vibration frequency in the vibration directions. This may cause the angular velocity sensor to output an unnecessary signal.